Fluid-flow machine

ABSTRACT

A fluid-flow machine comprises an essentially disk-shaped rotor with flow channels whose inlet openings and outlet openings are differently spaced respectively from the axis, the flow direction of the channels being axial near the axis but predominantly tangential remote from the axis. The rotor has curved overflow edges which close the inner flow-channel boundary surfaces and which face the rotor axis in the region of the rotor openings remote from the axis. The overflow edges form a direct connection over the entire periphery, interrupted only by the channelseparating wall thickness of the rotor - between the predominantly tangential channel portions at the rotor openings remote from the axis on the one hand, and the predominantly radial channel portions in the middle region of the rotor on the other hand. The edges effect a directional change between axial and radial flow. The cross section of the flow channels in the rotor is narrower in the axial than in the radial direction in the region remote from the rotor axis, and this cross-sectional shape changes gradually toward the axis to a reversely dimensioned configuration having a larger width in the axial direction than in the radial direction.

United States Patent [191 Bachl [s41 FLUID-FLOW MACHINE [76] Inventor: Herbert Bachl, Turkenstr. 40, 8 Munich 13, Germany 22 Filed: June 22,1970

21 Appl.No.: 48,121

301 Foreign Application Priority Data June 20, 1969 Gennany ..P 19 33 070.2 July 15, 1969 Germany ..P 19 35 872.6 Apr. 30, 1970 Gennany ..P 20 21 260.6

[52] US. Cl. ..416/186, 415/178, 415/203, 415/215 [51] Int. Cl, ..F04d 29/38, FOld 5/08, F04d 7/00 [58] Field of Search ..4l5/l99 R, 205, 19, 415/202, 203, 69,143, 215; 416/213, 186,

[56] References Cited UNITED STATES PATENTS 963,378 7/l9l0 Lorenz ..4l6/l86 2,469,125 3/1949 Meisser ..416/l83 3,226,085 12/1965 Bachl ..4l5/199 R 3,286,984 11/1966 Bachl ..415/69 3,306,574 2/1967 Bachl ..4l5/ 143 3,444,817 5/1969 Caldwell ..4l5/215 FOREIGN PATENTS OR APPLICATIONS 1,325,267 3/1963 France ..416/183 51 Apr. 10, 1973 Primary Examiner-Henry F. Raduaao AttorneyCurt M. Avery, Arthur E. Wilfond, Herbert L. Lerner and Daniel J. Tick ABSTRACT A fluid-flow machine comprises an essentially diskshaped rotor with flow channels whose inlet openings and outlet openings are differently spaced respectively from the axis, the flow direction of the channels being axial near the axis but predominantly tangential remote from the axis. The rotor has curved overflow edges which close the inner flow-channel boundary surfaces and which face the rotor axis in the region of the rotor openings remote from the axis. The overflow edges form a direct connection over the entire periphery, interrupted only by the channel-separating wall thickness of the rotor between the predominantly tangential channel portions at the rotor openings remote from the axis on the one hand, and the predominantly radial channel portions in the middle region of the rotor on the other hand. The edges effect a directional change between axial and radial flow. The cross section of the flow channels in the rotor is narrower in the axial than in the radial direction in the region remote from the rotor axis, and this cross-sectional shape changes gradually toward the axis to a reversely dimensionedconfiguration having a larger width in the axial direction than in the radial direction.

11 Claims, 15 Drawing Figures 8 PATEHHU AFR 1 0 I975 SHEET U UF 4 FLUID-FLOW MACHINE My invention relates to fluid-flow machines, such as machines for converting fluid-flow energy into mechanical energy or, as in pumps, for applying mechanical energy to produce fluid flow, or to mechanical power-generating engines. More specifically, the invention is concerned with fluid-flow machines with at least one substantially disc-shaped rotor which has fluid-flow channels whose inlet openings are located at a distance from the axis of rotor rotation differing from the distance of the outlet openings, the channels being traversed by fluid-flow in a axial direction in the region near the axis, whereas the channels and openings more remote from the axis are traversed in a predominantly tangential direction with but a slight axial component. In such a rotor, the flow within the rotor wheel extends predominantly in a radia] direction.

It is an object of my invention, therefore, to improve fluid-flow machines of the above-outlined reducing the flow losses.

The invention is predicated upon the consideration that while retaining the flow directions in their given sequence, these flows must transfer from the relative speed to the absolute speed, the relative speed, with respect to a cross section perpendicular to the rotor axis, extending radially up to near the outer and inner boundary.

Taking this into account, it is a feature of my invention to provide the rotor of such a machine with overflow edges of rounded shape which closes the boundary faces of the flow channels facing the axis of rotation in the region of the rotor openings that are remote from the axis. The rounded overflow edges form a direct connection over .the entire periphery interrupted only by the wall thickness of the channel partitioning rotor structure between the rotor openings in the region remote from the axis, which openings are predominantly traversed tangentially by the fluid flow, on the one hand, and the predominantly radially flowtraversed middle region of the rotor. The connection thus provided by the overflow edges is such that, directly at the transition region of the rotor, there occurs a directional change between the axial flow direction and the radial flow direction. Furthermore, the cross-sectional shape of the flow channels is radially narrower and tangentially wider at localities remote from the axis, and is reversely dimensioned and hence wider in the axial direction than in the tangential direction at localities near the axis, the two cross-sectional shapes merging gradually with each other.

In the region remote from the axis, the outer boundary surface, which forms a radial transition curve from the radial to the tangential direction in similarity to the design at the inner rotor openings may merge in the outward direction with a rotor blade which is curved from the axial to the tangential direction but is considerably narrower in the radial direction, this blade constituting a boundary edge appertaining to the rotor openings remote from the axis.

Depending upon whether the fluid-flow machine is to operate as a working machine or as a power-generating machine, the radial partitioning walls between the fluid-flow channels are curved at the inlet and outlet openings in the forward or rearward direction respectively that is, they are curved either in the direction of rotation or in opposition thereto.

type toward According to another feature of my invention, the rotor openings remote from the axis may be so arranged at the lateral side of the rotor that the flow channels are covered or roofed-over in the radially outward direction and that any curvature of the partitioning walls merges with the boundary surface of the covering structure. In the region remote from the axis, the partitioning walls between the flow channels may merge into a rotor blade which is curved in an axialtangential direction, and which constitutes a boundary edge of the rotor opening. The rotor openings near the axis may also be designed for flow traversal in a direction having an additional tangential component inthe direction of rotation or in opposition thereto. The entire flow path of the machine stage, comprising a rotor and a guide wheel, may entirely or partially extend, in a cross section perpendicular to the axis, either as a connection of shallow curvature between respective tangents at the median diameters of the rotor openings, or as a reversing loop or distorted spiral for reversing the flow direction more than 360. Otherwise, the radial partitioning walls may be arranged entirely or partially in directions inclined or askew to the rotor axis.

Disc-shaped wide-wheel stages may be disposed between two rotor stages. The flow path in such an intermediate guide wheel, relative to a section perpendicular to the axis, may be an approximate mirror image of the flow path in the adjacent rotor.

Furthermore, one and the same rotor may be provided with at least two systems of flow channels disposed radially above one another and comprising correspondingly larger partitioning wall portions which are common to the two channel systems. In such cases, it is preferable to have the channels arranged in roofshingle fashion radially above one another in such a manner that-they are traversed, for example, by the same or also by different working media of respectively different pressures or different temperatures in the same or mutually opposed directions. In this manner, a particularly effective cooling of the flow channels, if traversed by hot working medium, can be obtained with the aid of the adjacent colder medium, and a reliable mechanical energy transfer from expansion channels tocompression channels may be secured by the partitioning walls which the two systems have in common. In this sense, the partitioning walls of an expansion channel located between two compression channels may be provided with cooling channels whereby the passage of branched-off flows of working medium from a higher pressure region of one of the two systems into a lower-pressure region of a second compressing system affords securing an additional cooling action.

The invention will be further explained with reference to the accompanying drawings which show embodiments of the invention in simplified, schematical representation with emphasis upon the essentials of the invention. Identical or mutually corresponding components are designated by the same reference characters in all of the illustrations. More specifically,

FIG. 1 shows schematically and in perspective, partly broken away, a portion of the rotor structure and stationary guide structure.

FIG. 2 is a partial lateral and partly sectional view of FIG. 1 taken along the line IIII and with the rotor uncovered.

FIG. 2a is a view similar to FIG. 2 of a modified form of the rotor.

FIG. 3 is a section through FIG. 2 taken along the line IIIIII.

FIG. 4 is a cross section of FIG. 2 in the peripheral direction of the rotor taken along the line IVIV.

FIG.- 4a is a view similar to FIG. 4 of the modified form of the rotorshown in FIG. 2a.

FIGS. 5 to 8 illustrate a second embodiment, the individual FIGS. 5, 6, 7 and 8 corresponding, as to the manner of illustration, to the above-described views and general contents shown in FIGS. 1 to 4 respectively.

FIGS. 9 to 12 illustrate a third embodiment in the same fashion, the individual illustrations of FIGS. 9, 10, 11 and 12 corresponding to FIGS. 1 through 4 respectively.

FIG. 13 illustrates partly in section a further embodiment by schematically showing a complete machine inclusive of its housing and the appertaining external fluid-flow lines.

In FIG. 1 the shaft of the illustrated machine rotor portion is denoted by 1. The rotor is shown uncovered so that only the rotationally symmetrical wall portion 2, part of the shroud 2' and the partitioning walls 3 between the individual fluid-flow channels are visible. This embodiment is a centripetally traversed power machine in which the working medium enters through a guiding device 4 or a suitable guide wheel whence it flows tangentially into the rotor from one axial (lateral) side of the rotor portion 2. The guide device 4 comprises suitable blades, ribs or other guiding elements which may form part of a stationary housing structure of conventional type or design, a housing structure generally suitable for embodiments as shown in FIGS. 1 to 4, FIGS. 5 to 8 or FIGS. 9 to 12 being described hereinafter with reference to FIG. 13.

As will be seen particularly from FIG. 3, the working medium enters into the rotor of FIG. 1 in the direction of the arrow 6, the flow direction being predominantly tangential with an only slight axial component. Within each flow channel 7 shown in FIG. 3, the flow is guided to change its direction to a radial flow up to the locality identified by a dot-and-dash line 8. Up to this locality the cross-sectional shape of the flow channel 7 varies in such a manner that an originally small width in the axial or radial direction and a large width in the tangential direction merge gradually into a larger width in the axial direction and a smaller width in the tangential direction. For example, the inlet opening 9 may be shaped essentially as a slot extending in a tangential direction, whereas the outlet opening from which the working medium issues in the direction of the arrow 11 in a axial direction, is shaped as a slot extending in a radial direction.

As will also be seen from FIG. 2, the outer opening 9 of each flow channel is designed as a slot whose tangential length is considerably larger than its radial length. In contrast thereto, the outlet openings 10 are designed as respective slots in the radial direction. That is, the

outlet openings are radially much longer than tangentially.

The flow channels are outwardly bordered by areas which are formed by the body of rotation 12. The inner surface 13, constituting the boundary face for each of the respective flow channels, has a double curvature. In the region of the openings 9 remote from the axis, the inner boundary face facing the axis of rotation, is closed by a rounded overflow edge 15 which also forms part of the rotor structure. This overflow edge forms, over the entire periphery interrupted only by the wall thickness of the partitions between the flow channels, constitutes a direct connection between the predominantly tangentially traversed openings remote from the axis of the rotor on the one hand and its predominantly radially traversed middle region on the other hand. The working medium entering through the slots is guided by this overflow edge to change its direction, namely, directly from the axial direction to the radial direction, whereas the tangential component of the relative speed, as the vectorial difference between the tangential component of the absolute speed and the peripheral speed, becomes very small. This design of the flow paths in the region remote from the axis affords keeping the flow losses slight and attaining a high degree of efficiency even at the lower speeds within the available high-speed range.

Such a design is essentially distinct from the heretofore known types of radial machines. whose rotor openings are also traversed in the region remote from the axis in a predominantly tangential direction of flow with an axial component, but in which the working medium is guided within the tangential region of the rotor partly in channels affected by high flow losses.

As will be recognized particularly from FIG. 3, the flow channels in the embodiment exemplified by FIGS. 1 to 4 are radially and gradually curved so that no centrifugal stresses occur. The partitioning walls 3 in the outward region, for example at the locality 16 in FIG. 2, may be curved in the peripheral direction in order to improve the directional change from the tangential to the predominantly radial flow. In a similar manner, a curvature may be given to the partitioning walls in the inward region closer to the axis, such as at the locality 17 in FIG. 2. The boundary faces of the flow channels then assume a cross-sectional shape similar to a forwardly curved blower blade or similar to a distorted Pelton wheel blade.

According to another feature of my invention, the partitioning walls may be given a design which cutwardly in the axial direction and in the sense of the rotation (arrow n) extends and merges into a blade which, however, is considerably narrower. This design is comparable to a principle of construction heretofore attempted, in modified form, for use in the transitional region near the axis of known radial-type machines. The embodiment first described is illustrated in FIGS. 2 and 4; the modification last described is shown in FIGS. 2a and 4a, the latter modification being characterized by the blade-like design of the partitioning walls at the outer periphery. It will be remembered that FIGS. 4 and 4a represents a top view along a section in the peripheral direction as compared with FIGS. 2 and 2a.

FIGS. 5, 6, 7 and 8 illustrate a modified embodiment in which the outer openings 9 of the rotor are located on a conical surface about the rotor axis, and in which these openings are traversed by fluid in a direction having an additional radial component (arrow 6). A radial roof-like covering over the openings cannot be provided in this modification. In spite of the stress caused additionally by centrifugal force, the curvature 16 of the blades (FIG. 6) is in accordance with the embodiment of FIGS. 1 to 4. The outer -boundary of the flow channels, designed as a rotational surface, has only a single curvature 18, as is particularly apparent from FIG. 7. In analogy to FIG. 2, FIG. 6 also indicates by a dotted line 19 the course of the absolute velocity of the flow in the rotor. The flow may issue in an axial direction from the rotor openings 10 close to the axis; however, the tangential component in the direction of rotation may also be retained as is schematically represented by the dotted line 20. On the other hand, it is also possible to have the flow pass in the direction opposed to the rotation, this being indicated by a dotted line 21. 1

A precisely axial transfer at the inner openings of the motor is not desirable because this would make it difficult or infeasible to give an adjacent guide-wheel disc a narrow dimension in the axial directiomWith respect to the total flow path in a machine stage, consisting of a rotor and a guide wheel, which flow path need not be completely present in single-stage machines, two fundamental variants are available. This is apparent from the embodiment illustrated in FIGS. 9, 10, 11 and 12.

In FIG. 10 the flow path in the rotor is schematically represented by a dotted curve 19 and the path in the guide wheel by a broken-line curve 22. In a variant according to the flow course 23, a slightly curved flow path, in cross section, connects respective tangents to the median outer diameter of the inner and outer rotor openings. The flow path is long, the curvature radius is large. In the variant represented by the curve 21, there occurs a reversal in flow direction in the rotor and another such reversal in the guide wheel. The curvature radius increases in the inward direction and is smallest in the reversing loop. The entire reversal per stage is larger than 360. However, the specific power is larger than with the variant represented by the curve 20. In the embodiment illustrated in FIGS. 9 to 12, the radial boundary walls 3 are more strongly curved in order to provide for a tangential component opposed to the rotational direction in the transition region near the axis. Besides, the boundary walls 3 are arranged in a direction inclined or askew to the rotational axis to permit reducing the curvature radius in the axial direction. The illustrated arcuate shape at the outer periphery in the region 16 is not absolutely necessary; on the other hand, an inclined positioning of the radial partitioning walls can also be applied to a machine design otherwise corresponding to FIGS. 1 to 4. The inclined position may also be limited to the outer region of the rotor, and the partitioning walls may be given a spacial twist similar to the end blades of large axial machines.

Machines according to the invention exhibit various advantages over the known fluid-flow machines. In the first place, machines according to the invention can be given a more compact design. They afford an optimal utilization of space, together with the possibility of securing good efficiency values also at lower speeds within the available high-speed range of operation. With conventional high-pressure axial machines, a space remains between the blades and the machine shaft, which space must be filled with material for transferring energy to or from the shaft; hence this space cannot be utilized for the conversion between flow energy and mechanical energy. Radial machines require additional space in the radial direction outside of the rotor for accommodating guiding elements or spiral housings. In a multistage radial machine, it is furthermore necessary to provide space in radial and axial directions for accommodating the flow reversals which, in cross section through the axis, change the flow direction of the workingmedium on the outer side by an angle of 180 and on the inner side by an angle of in most cases, therefore, multi-stage radial machines do not attain the high degree of efficiency obtainable with multi-stage axial machines. In contrast, the invention makes it possible that the available space in the axial and radial direction in the rotor and in the guide wheel can be utilized in optimal relation to the energy conversion and to the transfer of energy from and to the machine shaft.

The invention affords further advantages by the possibility of effectively cooling the flow channels that are traversed by a working medium of high temperature. Thus, expansion energy may be transferred directly to flow channels serving to compress a working medium. It is known as such to arrange working channels and cooling channels, or expansion and compression channels, in one and the same rotor. Heretofore, the cooling has been effected by having the cooling channels pass through the axial blades in a direction perpendicular to the flow of the working medium; and, so far, attempts toward uniform and optimal distribution of the heat flow or the mechanical energy having failed. In contrast, the invention affords giving channels that are traversed by different or the same working media and have different pressures or different temperatures, a staggered arrangement in roof-shingle fashion so as to be located radially above one another. In such a channel arrangement, each two mutually adjacent flow channels have a partitioning wall in common along a relatively large portion of their respective flow paths. This secures a uniform transfer of the heat or the mechanical energy over a large area.

The last-mentioned features are exemplified in the embodiment shown in FIG. 13. Cooling or compression channels 26 and 27 are located in the rotor above and below the expansion channel 25 traversed by the working medium. The stator or housing of the machine is provided with guiding elements 28, 29 and 30 for the respective rotor channels 25, 26 and 27. Radial and axial surface areas of the rotor and housing are available for accommodating gaskets or seals 31, 32, 33 and 34.

The partitioning walls between the expansion channels of the rotor are additionally and effectively cooled by embedding cooling channels 35, 36, 37 in the partitioning walls. The cooling channels permit given quantities of coolant to flow from different regions of the one compression channel system into lower-pressure regions of the other system.

This particular embodiment is a machine operating in an open gas-turbine process. The hot gases of the firing chamber 38 pass through the guiding device 28 and leave the flow channel 25 through a flow guide 39 in the stator (housing). The turbine waste gases then pass through a conduit 40 to a heat exchanger 41. The inducted combustion air is compressed in the channels 26 and 27 of the rotor, whereafter it passes through a duct 42 to the heat exchanger 41 operating as an air preheater for the combustion air. The combustion air thus preheated passes through a duct 43 to the firing chamber 38 together with the fuel supply through the fuel inlet duct 44. Such a machine, of course, may be given a multi-flue or multi-stage design with intermediate cooling or intermediate superheating between the individual stages.

Upon a study of this disclosure, it will be apparent to those skilled in the art that my invention permits of a great variety of modifications and various uses, and may be given embodiments other than those particularly illustrated and described herein,.without departing from the essential features of my invention and within the scope of the claims annexed hereto.

I claim: 7

l. Fluid flow machine, comprising an essentially discshaped rotor having lateral sides and radially extending channel-partitioning walls defining therebetween flow channels and said channels having inlet openings and outlet openings which are differently spaced respectively from the rotor axis in the region of the rotor lateral sides, said channels forming a flow path having a section extending-in axial direction near said axis, a section extending predominantly tangentially with a slight axial component at a location remote from said axis, and a section connected between said axially extending section and said predominantly tangentially extending section and extending in radial direction, a rounded overflow edge facing toward said rotor axis in the region of said channel section having openings that are remote from said axis,'said edges closing the inner flow-channel boundary surfaces and forming substantially over the entire periphery except for the thickness of said channel-partitioning walls of the rotor, said direct radial connection between said predominantly tangentially directed channel portions at said rotor openings remote from said axis and the predominantly radially directed channel portions in the middle region of the rotor defining a flow reversing outer surface in said channel effecting a directional change between the axial and the radial flow directions in the immediate vicinity of the radial transition connecting section, said flow channels having a cross-sectional shape, in the opening tosaid predominantly tangential section, which is narrower in axial direction than in circumferential direction thereof, the cross-section of said flow-channels gradually merging toward the axis with a shape, in the opening to said axial section, which is wider in the axial direction thereof than in the circumferential direction thereof.

2. In a fluid-flow machine according to claim 1, said channel-partitioning walls comprising rotor blades and having in the region remote from the rotor axis an outer boundary surface which forms a radial transition of curved shape extending from the radial to the tangential direction, the channels from the inner rotor openings toward the outer opening forming a transition to respective ones of said blades, said latter transition being curved from the axial to the tangential direction, said blades being radially considerably narrower .than said inner rotor openings and forming a boundary edge for the respective rotor openings remote from the axis.

3. In a fluid-flow machine according to claim 1, the

radial partitioning walls of said rotor between respective flow channels being curved at said inlet openings 11'! the forward direction for use of the machine as pump.

4. In a fluid-flow machine according to claim 1, wherein said outlet openings are the radially outer openings said partitioning walls of said rotor between respective channels being curved at said outlet openings in the rearward direction for use of the machine as an engine. 7

5. In a fluid-flow machine according to claim 1, said rotor openings in the region remote from said axis being arranged at an axial side of the rotor so that the flow-channels have a covering in the radially outward direction.

6. In the fluid-flow machine according to claim 5, the partitioning walls between said flow-channels having a curvature merging with the boundary face of the covermg.

7. ln a fluid-flow machine according to claim 5, said rotor having blades whose shape is curved in an axialtangential direction and which form extensions of said partitioning walls between said flow-channels in the region remote from said axis, said blades forming respective boundary edges of the rotor openings.

8. In a fluid-flow machine according to claim 7-, the outer tangential boundary face of said flow-channels having a single curvature.

9. In a fluid-flow machine according to claim 18, said radial partitioning walls between said flow channels extending at leastpartially in a direction inclined to said rotor axis.

10. Fluid-flow machine according to claim 1 comprising two systems of flow-channels arranged in the same rotor above one another, said two systems of channels having partitioning wall portions in common with each other.

11. In a fluid-flow machine according to claim 10, wherein the flow channels in each of said systems comprise expansion channels and compression channels said flow-channels being arranged above another in roof-shingle-fashion so that said common partitioning wall portions are capable of transferring mechanical energy from said expansion channels to said compression channels of said respective channel systems.

t i i i i 

1. Fluid flow machine, comprising an essentially disc-shaped rotor having lateral sides and radially extending channelpartitioning walls defining therebetween flow channels and said channels having inlet openings and outlet openings which are differently spaced respectively from the rotor axis in the region of the rotor lateral sides, said channels forming a flow path having a section extending in axial direction near said axis, a section extending predominantly tangentially with a slight axial component at a location remote from said axis, and a section connected between said axially extending section and said predominantly tangentially extending section and extending in radial direction, a rounded overflow edge facing toward Said rotor axis in the region of said channel section having openings that are remote from said axis, said edges closing the inner flow-channel boundary surfaces and forming substantially over the entire periphery except for the thickness of said channelpartitioning walls of the rotor, said direct radial connection between said predominantly tangentially directed channel portions at said rotor openings remote from said axis and the predominantly radially directed channel portions in the middle region of the rotor defining a flow reversing outer surface in said channel effecting a directional change between the axial and the radial flow directions in the immediate vicinity of the radial transition connecting section, said flow channels having a cross-sectional shape, in the opening to said predominantly tangential section, which is narrower in axial direction than in circumferential direction thereof, the cross-section of said flow-channels gradually merging toward the axis with a shape, in the opening to said axial section, which is wider in the axial direction thereof than in the circumferential direction thereof.
 2. In a fluid-flow machine according to claim 1, said channel-partitioning walls comprising rotor blades and having in the region remote from the rotor axis an outer boundary surface which forms a radial transition of curved shape extending from the radial to the tangential direction, the channels from the inner rotor openings toward the outer opening forming a transition to respective ones of said blades, said latter transition being curved from the axial to the tangential direction, said blades being radially considerably narrower than said inner rotor openings and forming a boundary edge for the respective rotor openings remote from the axis.
 3. In a fluid-flow machine according to claim 1, the radial partitioning walls of said rotor between respective flow channels being curved at said inlet openings in the forward direction for use of the machine as pump.
 4. In a fluid-flow machine according to claim 1, wherein said outlet openings are the radially outer openings said partitioning walls of said rotor between respective channels being curved at said outlet openings in the rearward direction for use of the machine as an engine.
 5. In a fluid-flow machine according to claim 1, said rotor openings in the region remote from said axis being arranged at an axial side of the rotor so that the flow-channels have a covering in the radially outward direction.
 6. In the fluid-flow machine according to claim 5, the partitioning walls between said flow-channels having a curvature merging with the boundary face of the covering.
 7. In a fluid-flow machine according to claim 5, said rotor having blades whose shape is curved in an axial-tangential direction and which form extensions of said partitioning walls between said flow-channels in the region remote from said axis, said blades forming respective boundary edges of the rotor openings.
 8. In a fluid-flow machine according to claim 7, the outer tangential boundary face of said flow-channels having a single curvature.
 9. In a fluid-flow machine according to claim 18, said radial partitioning walls between said flow channels extending at least partially in a direction inclined to said rotor axis.
 10. Fluid-flow machine according to claim 1 comprising two systems of flow-channels arranged in the same rotor above one another, said two systems of channels having partitioning wall portions in common with each other.
 11. In a fluid-flow machine according to claim 10, wherein the flow channels in each of said systems comprise expansion channels and compression channels said flow-channels being arranged above another in roof-shingle-fashion so that said common partitioning wall portions are capable of transferring mechanical energy from said expansion channels to said compression channels of said respective channel systems. 